Comprehensive Overview of Nervous System Structure and Functions

A set of vocabulary flashcards covering the organization, cellular components, and physiological mechanisms of the human nervous system based on the lecture notes.

Central Nervous System (CNS)

Comprising the brain and spinal cord located within the dorsal body cavity, it serves as the integration and control center by interpreting sensory input and dictating motor output.

Peripheral Nervous System (PNS)

Consisting mainly of nerves that extend from the brain and spinal cord, it functions as communication lines linking the CNS to the rest of the body.

Sensory Input

The function of the nervous system that gathers information from internal (visceral) and external (somatic) sensory receptors about changes in the environment.

Integration

The process by which the nervous system interprets sensory input to form perceptions, thoughts, and decisions.

Motor Output

The activation of effector organs such as muscles and glands to produce responses like muscle contraction or secretion.

Sensory (Afferent) Division

The subdivision of the PNS that conveys impulses from sensory receptors to the CNS, including somatic and visceral sensory fibers.

Motor (Efferent) Division

The subdivision of the PNS that transmits impulses from the CNS to effector organs like muscles and glands.

Somatic Nervous System

A part of the motor division that provides voluntary control over skeletal muscles.

Autonomic Nervous System (ANS)

A part of the motor division that provides involuntary control over smooth muscles, cardiac muscles, and glands.

Sympathetic Division

A branch of the Autonomic Nervous System that mobilizes body systems during activity, often referred to as the "Fight or Flight" response.

Parasympathetic Division

A branch of the Autonomic Nervous System that conserves energy and promotes housekeeping functions during rest, often referred to as "Rest and Digest."

Cell Body (Soma)

The part of a neuron containing the nucleus and organelles such as the RER for protein synthesis and mitochondria for energy production.

Dendrites

Branched processes of a neuron that receive incoming signals from other neurons or sensory receptors.

Axon

A long neuronal process that transmits action potentials away from the cell body toward other neurons or effectors, beginning at the axon hillock.

Multipolar Neurons

Neurons with one axon and two or more dendrites; the most common type, including motor neurons and CNS interneurons.

Bipolar Neurons

Neurons with one axon and one dendrite, found in specialized sensory organs like the retina and olfactory epithelium.

Unipolar/Pseudounipolar Neurons

Neurons with a single process that bifurcates into peripheral and central branches, typical of sensory neurons for touch and proprioception.

Anaxonic Neurons

Neurons with many dendrites but no true axon, primarily located in the CNS to regulate nearby electrical activity.

Astrocytes

The most abundant CNS neuroglia that support neurons, regulate the chemical environment, and help form the blood-brain barrier.

Microglial Cells

Small, immune-like cells in the CNS that monitor neuron health and phagocytize microorganisms or debris.

Oligodendrocytes

Glial cells that form insulating myelin sheaths around nerve fibers specifically in the Central Nervous System.

Satellite Cells

Supporting cells in the Peripheral Nervous System that surround and support neuron cell bodies within ganglia.

Schwann Cells

Cells that wrap around peripheral nerve fibers to form myelin sheaths, facilitating rapid electrical conduction in the PNS.

Myelin Sheath

A lipid-rich insulating layer that wraps around axons to increase the conduction velocity of electrical impulses.

Nodes of Ranvier

Gaps in the myelin sheath where the axonal membrane is exposed, allowing for saltatory conduction.

Epineurium

The outermost connective tissue layer that surrounds an entire nerve.

Perineurium

The connective tissue layer that surrounds fascicles, which are bundles of axons within a nerve.

Endoneurium

The delicate connective tissue layer that wraps around individual axons.

Graded Potentials

Small, localized changes in membrane potential, occurring mainly in dendrites and cell bodies, whose strength depends on stimulus intensity.

Temporal Summation

The combining of multiple graded potentials triggered by multiple signals from the same presynaptic neuron over time.

Spatial Summation

The combining of multiple graded potentials triggered by simultaneous signals from different presynaptic neurons.

Action Potentials

Rapid, large depolarizations of the membrane potential that propagate along the axon for long-distance communication.

Threshold

The membrane potential level, typically approximately $-55\,mV$, required to initiate an action potential.

Voltage-gated channels

Ion channels that open or close in response to changes in membrane potential; essential for the various phases of an action potential.

Depolarization

The phase of an action potential where voltage-gated $Na^+$ channels open, allowing $Na^+$ influx and making the membrane potential more positive.

Repolarization

The phase where $Na^+$ channels inactivate and voltage-gated $K^+$ channels open, allowing $K^+$ to exit and restoring negative membrane potential.

Hyperpolarization

A temporary state where $K^+$ channels remain open longer than necessary, making the inside of the cell more negative than the resting potential.

Saltatory Conduction

The rapid jumping of action potentials from one node of Ranvier to the next along a myelinated axon.